Topic Contents

Contraction Stress Test

Test Overview

A contraction stress test checks to see if
your unborn baby (fetus) will stay healthy during the
reduced oxygen levels that normally occur during contractions when you are in
labor. This test includes
external fetal heart monitoring. The test is done when you are
34 or more weeks pregnant.

During a uterine contraction, the
blood and oxygen supply to your baby drops for a short time. This is not a
problem for most babies. But the heart rate of some babies gets slower. This
change in heart rate can be seen on the external fetal monitoring
device.

For a contraction stress test, the hormone oxytocin is
given to you in a vein (intravenously, or IV) to cause labor
contractions. You may also massage your nipples. This tells your body to
release oxytocin. If your baby's heart rate slows down (decelerates) in a
certain pattern after a contraction instead of speeding up (accelerating), your
baby may have problems with the stress of normal labor.

A
contraction stress test is usually done if you have an abnormal nonstress test or
biophysical profile. A biophysical profile uses
ultrasound during a nonstress test to measure a series
of physical characteristics of your baby. You may have more than one contraction stress test during your
pregnancy.

Some doctors may do a biophysical profile or a
Doppler ultrasound test instead of a contraction
stress test.

Why It Is Done

A contraction stress test is done to
check:

If your baby will stay healthy during the
reduced oxygen levels that normally occur during contractions during
labor.

A contraction stress test may be done when results from a
nonstress test or a biophysical profile are not in the normal range.

How To Prepare

You may be asked to not eat or drink
for 4 to 8 hours before the test. Empty your bladder before the test.

If you smoke, stop for 2 hours before the test, because smoking can lower
your baby's activity and heart rate.

You will be asked to sign a consent form that says you understand the risks of the test and agree to have it done.

Talk to your doctor about any
concerns you have regarding the need for the test, its risks, how it will be
done, or what the results will mean. To help you understand the importance of
this test, fill out the
medical test information form(What is a PDF document?).

How It Is Done

A contraction stress test may be done
in your doctor's office or hospital by a
family medicine doctor or an
obstetrician and a trained laboratory technician or
nurse. You usually do not need to stay overnight.

During the test,
you will lie on a bed with your back raised. You will be tilted a little to
your left side so you will not have pressure on the blood vessels in your
belly. Two belts with sensors will be placed around your belly. One belt holds
the sensor that records your baby's heart rate; the other sensor measures your
uterine contractions. Gel may be used on your skin with the heart rate sensors.
The sensors are hooked to a recording unit. The heart rate monitor may be moved
if your baby changes position. Your baby's heart rate and your contractions are
recorded for 10 minutes. Your blood pressure and other vital signs are also
recorded.

The hormone oxytocin is given in a low dose and
increased until you have three contractions within 10 minutes, each one lasting
longer than 45 seconds. Or you may be asked to massage one of your nipples by
hand to start contractions. If you don't have a second contraction within 2
minutes of the first, you will massage your nipple again. If contractions do
not occur within 15 minutes, you will stimulate both nipples.

After the test, you will be watched until your contractions go away or
slow down to what they were before the test. A contraction stress test may take
2 hours.

How It Feels

You may need to lie on your left side for
the test. This position may be uncomfortable or painful when you are having
labor contractions. The belts holding the sensors may be uncomfortable. Most
women say this test is uncomfortable but not painful.

Risks

Fetal heart monitoring may indicate that your baby is having problems when your baby is actually healthy. Fetal heart
monitoring can't detect every type of problem, such as a birth defect.

The risks from having oxytocin include:

Causing labor to start earlier than your
expected delivery date.

Causing prolonged contractions that may
cause problems with your baby. The contractions usually stop when the oxytocin
is stopped. You may be given a medicine to stop the contractions. If in the
very rare case that your contractions do not stop, your doctor may recommend
delivery.

Results

A contraction stress test checks to see
if your unborn baby (fetus) will
stay healthy during the reduced oxygen levels that normally occur during
contractions when you are in labor.

Results of the test tell your
baby's health for 1 week. The test may need to be done more than once during
your pregnancy.

Your
baby's heart rate does not get slower (decelerate) and stay slow after the
contraction (late decelerations). Note: There may be a
few times during the test when your baby's heart rate decelerates, but it
doesn't stay slow so it is not a problem.

If three contractions
occur during a 10-minute period of nipple stimulation or oxytocin infusion and
there are no late decelerations in your baby's heart rate, your baby is
expected to be able to handle the stress of labor.

Abnormal:

Abnormal test results are called positive.

Your
baby's heart rate gets slower (decelerates) and stays slow after the
contraction (late decelerations). This happens on more than half of the contractions.

Late decelerations may
mean that your baby will have problems during normal labor.

What Affects the Test

Reasons you may not be able to
have the test or why the results may not be helpful include:

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use.
How this information was developed to help you make better health decisions.